DESCRIPTION: (Applicant's Abstract) Multiple studies have attempted to explore the relationship between substance use and participation in sexual behaviors which place an individual for HIV infection. Even though methodological shortcomings have precluded researchers from determining a direct causal link between substance use and HIV sexual risk behaviors, there is some level of agreement that the relationship between these two behaviors is indeed complex and in need of further study. This two year cross-sectional study will attempt to elucidate further the complex relationship between substance use prior to sexual activity and HIV sexual risk behaviors among African-American homeless adolescents, a group of youth who are at extremely high risk for HIV infection. In addition, the contributory role of negative affective states on this relationship will be explored. African-American homeless adolescents will be recruited from a non-residential drop-in center for homeless youths and will be asked detailed questions about their substance use, sexual activity, and substance use prior to sexual activity. They also will be asked to complete measures which will assess three negative affective states (i.e., anxiety, depression and loneliness) Participants will then be interviewed using the Timeline Follow-Back (TLFB) method which assesses event-level sexual and substance abuse episodes which occurred in the previous month. The presence of various contextual factors and negative affect will also be assessed in the TLFB interview. In order to explore the complexity of the substance use/HIV sexual risk behavior relationship, analyses will be conducted for each type of substance used and for each type of sexual partner (i.e., primary vs. casual). In addition, the contributory role of negative affect, as well as the potential moderating effects of life experiences and demographics, will be explored